Brake Pistons do not move, tried everything.

[Tom_91]

Hi Guys,

I've took the front brake off and it looks like pistons do not want to move at all when pumping the front brake leaver.

I've noticed that I've lost fluid from my head cylinder and replaced it, however after pumping fluid in from my head cylinder the piston didn't move at all.

The fluid is definitely pumped into Calliper, there is no leakage now but the piston seem to be stuck completely.

I've forced them into a 'home' position (fully retracted) with no movement at any point.

Would you guys b able to think of what the issue could be?

Cheers,
Tom

[Wafer_Thin_Ham]

Take them apart and clean them?
____________________
My Flickr

[Itchy]

[Pete.]

What you call 'head cylinder' is the master cylinder. The oil is held in the reservoir.

Seems if you pushed the caliper pistons back, then they are moving. I think that what you mean to say is that they aren't moving out when you squeeze the lever on the master cylinder. Since the master cylinder is pumping oil, which must be going somewhere, and the pistons aren't moving there must be air in the system. Bleed the front brakes.
____________________
a.k.a 'Geri'

132.9mph off and walked away. Gear is good, gear is good, gear is very very good

[Rogerborg]

If bleeding doesn't sort it, your master cylinder seals may be shot.

What bike, how old, how many miles, and have you done any very hard braking recently?
____________________
Biking is 1/20th as dangerous as horse riding.
GONE: HN125-8, LF-250B, GPz 305, GPZ 500S, Burgman 400 // RIDING: F650GS (800 twin), Royal Enfield Bullet Electra 500 AVL, Ninja 250R because racebike

[bikenut]

Piston/caliper corrosion making piston movement really really really difficult.

Hot water can help free of a stuck/stiff piston but it must be dried/lubed straight away after, else more corrosion, so perhaps mums hair drier for the heat.

Stuck/corroded in pistons can be freed off even with some air in the system.

Once piston has moved out as much as you dare without it popping out, clean off corrosion, lube and gently g clamp back in, repeat until piston is free.

If multi piston, g clamp others and work on one piston at a time, do not allow it to pop out!!

Pics of caliper/calipers, master cylinder and fluid.

Wood, brake fluid ( for lube, you know it can be a brilliant paint stripper ), g clamp/s, patience, rags, wire brush, pictures, pictures, pictures!!

see cmsnl for the exploded views of your bike and brakes.

Corroded piston hydraulic seal face, corroded area between caliper hydraulic seal and dust seal. master cylinder strip down clean reassembly with new parts and Fluid.

Red rubber grease.

Clean caliper pistons in a clean caliper bore will drop in and drop out, red rubber greased new seal and piston will be a push fit with thumb pressure. Any slide pins?? pics pics pics.
____________________
nuts about bikes

[stinkwheel]

Sounds like you need to bleed the air out.

If the lever has no resistance, either the master cylinder piston seal is dead or you need to bleed the air out of the system.

If the lever moves a little then goes solid, your pistons are seized. However, the pressure exerted by a hydraulic brake system is such that I'd expect even pistons that have been practically welded in place by corrosion to move with a good firm pull on the lever.
____________________
“Rule one: Always stick around for one more drink. That's when things happen. That's when you find out everything you want to know.”
I did the 2010 Round Britain Rally on my 350 Bullet. 89 landmarks, 3 months, 9,500 miles.

[Fin]

Can't you read the title guys? HE'S TRIED EVERYTHING

[Ed Case]

Buy new stuff ?.

[Major Doss]

[stinkwheel]

[bikenut]

Doc whatever posted:

bikenut wrote:

see cmsnl for the exploded views of your bike and brakes.

Oh dear. I was so expectecting to be a better forum member..

Red rubber grease.

Woo! I did it.


ftfy foc

It is annoying when people advise the use of brake fluid on brake seals, so well done.


ftfy foc

It is annoying when people advise the use of brake fluid on brake seals, so well done.



what I actually wrote :

Piston/caliper corrosion making piston movement really really really difficult.

Hot water can help free of a stuck/stiff piston but it must be dried/lubed straight away after, else more corrosion, so perhaps mums hair drier for the heat.

Stuck/corroded in pistons can be freed off even with some air in the system.

Once piston has moved out as much as you dare without it popping out, clean off corrosion, lube and gently g clamp back in, repeat until piston is free.

If multi piston, g clamp others and work on one piston at a time, do not allow it to pop out!!

Pics of caliper/calipers, master cylinder and fluid.

Wood, brake fluid ( for lube, you know it can be a brilliant paint stripper ), g clamp/s, patience, rags, wire brush, pictures, pictures, pictures!!

see cmsnl for the exploded views of your bike and brakes.

Corroded piston hydraulic seal face, corroded area between caliper hydraulic seal and dust seal. master cylinder strip down clean reassembly with new parts and Fluid.

Red rubber grease.

Clean caliper pistons in a clean caliper bore will drop in and drop out, red rubber greased new seal and piston will be a push fit with thumb pressure. Any slide pins?? pics pics pics.



Doc whatever, dont know what the ftfy foc means, modern kids babble chat probably.

And,

Just what do the seals in your master cylinder etc. "live" in, mineral oil?

Original poster Tom, how you getting on? ?? pictures please
____________________
nuts about bikes

[Teflon-Mike]

If the master-cylinder reservoir was empty.. I'd want to know why, before anything else.

Pushing the pistons back all the way into the caliper body is usually a very bad idea on anything but a brand new caliper assembly.

The pistons, gradually creeping out of the caliper to compensate for pad wear, get covered in brake dust; add rain-water and possibly some road-salt; and the result is a quite corrosive mixture.

This causes the pistons, that are usually hard-chromed steel, like the fork stanchions to rust, and the chrome to pit and flake, depending on how bad they are allowed to get.

Now add road grime to the brake dust, and the rust, and you have a rather nasty 'grinding past' around the piston, which as it corrodes takes on the texture of sand-paper rather than glass...

Add the two together, and what you have is a perfect system for wearing away the rubber seals around the piston as the piston moves in and out, that very small distance it travels under normal braking operation.

THEN when you get to the point that the brake pads have worn out...

To fit new ones between the disc and the caliper body, you have to push the pistons back into the caliper body.. do that without cleaning & inspecting the pistons first, and you are likely to a) grind a load of rubber off the seals when you push them back in, b) push a load of shit past and or under the seals with the piston, so that the seal either wont, or wont for long, as the crap trapped under it holds it away from the metal its trying to seal against and or adds to the abrasive action wearing it away double time.

And like I say... brake fluid cant simply 'dissapear'... it HAS to go some-where.... and the seals in the caliper are a pretty likely suspect.

Master cylinder seals are next.. and not shoving fluid down the pipe to the caliper, adds to the suspicion...

But, putting new fluid into an empty reservoir, and not bleeding it through to remove air from the pipes, means that basically you haven;t got a clue what's going on... or what you are doing.

In which case, STOP and give the job to some-one who DOES.....

Brakes are ONE thing you really don't want to fuck'up from numptiness, they really aren't.
____________________
My Webby'Tef's-tQ, loads of stuff about my bikes, my Land-Rovers, and the stuff I do with them!
Current Bikes:'Honda VF1000F' ;'CB750F2N' ;'CB125TD ( 6 3 of em!)'; 'Montesa Cota 248'. Learner FAQ's:= 'U want to Ride a Motorbike! Where Do U start?'

[andym]

Have you tried removing the caliper, putting one of the bolts that hold it in place where you removed the banjo bolt, cracked open the bleed nipple and attached a foot pump (or airline), stick a thin piece of wood in as you would be amazed how far it will shoot a piston (and an extremely loud pop too)

[Fizzer Thou]

Here is how I deal with stuck pistons.

I use a spare master cylinder bolted to a spare handlebar held in a vice.Then I connect them together and bleed the system.

https://i666.photobucket.com/albums/vv23/WiNot_Rhencullen/Workshop/20160527_105059_zpsalhacskw.jpg

Gradually the pistons begin to move,no matter how stuck they are.Air would not move these as they were too seized in place

https://i666.photobucket.com/albums/vv23/WiNot_Rhencullen/Workshop/20160527_105047_zpswn81teto.jpg

The more the pistons pumped out,the thinner I made the stopper plate

https://i666.photobucket.com/albums/vv23/WiNot_Rhencullen/Workshop/20160527_105420_zpsggxlr1ts.jpg
https://i666.photobucket.com/albums/vv23/WiNot_Rhencullen/Workshop/20160527_105742_zpsfso5tn6d.jpg

Until the pistons were all of the way out

https://i666.photobucket.com/albums/vv23/WiNot_Rhencullen/Workshop/IMG-20160527-WA0004_zpsjdadzxjg.jpeg
https://i666.photobucket.com/albums/vv23/WiNot_Rhencullen/Workshop/IMG-20160527-WA0006_zps5rtqu2va.jpeg

Then it was just a question of carefully hooking out the dust and distortion seals,cleaning up the ring lands,using red seal grease or new brake fluid to lubricate the seals and reassembling the caliper.

If the pistons are as dirty as in the second or third picture,it is not worth just cleaning up the leading edge.Far better to pop out the pistons and clean everything.Otherwise the caliper will need more attention within a very short period of time.

If the seal lands as as bad as these that I removed from my FJ1200,then the pistons and seals will definitely needed cleaning

https://i1073.photobucket.com/albums/w384/Rhencullen5/FJ1200/20150729_105552_zpsus44loof.jpg
https://i1073.photobucket.com/albums/w384/Rhencullen5/FJ1200/20150729_105627_zpsgzbramcg.jpg
____________________
Just talk bikes.What else is there?

Always have a 'Plan B'

[Islander]

As above, bleed the system and use hydraulic pressure to drive the piston out.

[Major Doss]

I would use red rubber grease for it's non hygroscopic properties. For a piece of bike that has to deal with all manner of crap thrown at it, why would you give corrosion a headstart?

Brake fluid-moisture-corrosion-knackered seals-bound pistons. Repeat ad infinitum.

Other 'fiche sites are available, not just specifically one overpriced Dutch firm.

[bikenut]

As well as being brake seal/fluid friendly ( fluid dependant? ) , try castrol lm and see what happens!


Brake fluid-moisture-corrosion-knackered seals-bound pistons. Repeat ad infinitum. cos thats the process. Alloy corrodes, even stainless steel will etch etc..

Yeah, ride thru fords and pressure wash to your hearts content.

cmsnl is vast and free, but you don't have to buy from there do you?

Sorry cmsnl, but we have, and will again.

Still no answer about the kids babble and fluid/seal interface?

As to heat, warm the alloy so its expands a bit, a bit faster than the piston material, so piston can move more easily/at all.

With the hydraulics still plumbed, i place the caliper in a bucket of hot water, count to 3 then pump away, piston moves quite quickly and pop out. The stuff I have to deal with is usually badly corroded, needing new piston and seals, time with a dremel type wire wheel to get ride of all the alloy corrosion, cleaned cleaned cleaned and inspected, if ok, reassembled with new parts, then onto the master cyl.

Wow, if the stuff I have to deal with is a "good" as those fizzer, i would be well happy.

When m/cylinder is done ( remember that tiny little hole, the recouperating port, to allow the brakes to "release", unless its blocked!! ( cleared either mechanically ( less than 0.6mm hole) or by pressure ) a plumbed in caliper, use "reverse" hydraulic pressure, but be ready for the long lasting "jet" of fluid!!! ) its refitted to the bike, hose attached at that end, and fluid allowed to syphon/flow by gravity to caliper end of hose, cleaning it of old fluid as it does so.

Priming the m/cylinder is easy if bore has been "WETTED" with fluid before the unit was assembled, so piston etc. has a full non sticking, lubed bore to travel in.

Remember its a pump, so finger and thumb on caliper end banjo, and pump till air is pushed out, then connect to caliper and gravity prime till no more air, then normal pumping/nipple fiddling till bleed .

Just assume brake fluid is a good paint stripper/pad fucker upper etc so keep it way from the brakes, you dont lube brakes, unless its tractor type etc etc etc.....

pictures can be misleading/deceaving, would i re use those pistons and seals, no . want to know why??



how you getting on tom??
____________________
nuts about bikes